Yes, just enable the 'Add reading time tags on Pocket' setting in your
settings for Read Ruler.
With this enabled whenever Read Ruler updates your list of Pocket articles it will automatically add a tag for reading time to each article.

Note that you need to open Read Ruler in your browser for it to update your list of Pocket articles.

Read Ruler is made by
Chris Pederick.
Chris is a web developer originally from London, England, but now living in San Francisco, California.
He is a Director of Engineering at
Bleacher Report.
He is also known for his browser extensions—Web Developer
and
User Agent Switcher—which
he writes in his spare time and distributes for free.